The hub cap shown in Figure 2 is a 3D printed part. It
consists of three posts that are meant to insert into
mounting holes in the wheel tire. The holes in the posts are
.089” in diameter and should be tapped with a #4-40 tap.

The overall diameter is 1.7”, so you should be able to print
four or more on most 3D printers. If you are printing in
PLA, it is highly recommended that you print at least three
wheels to keep the posts from overheating and melting.

Wheel Geared Hub

The geared hub shown in Figure 3 is driven by either
the motor or idler gears. It is attached to the hub cap and
tire assembly via four #4-40 x 3/8” machine screws. While
you can print more than one of these at a time, it is
recommended that you print only one at a time to keep the
gear as accurate and clean as possible.

This time, I’ll go over the wheels,
gears, and chassis parts for our
Plastic Bot of Descruction (PBOD).

The STL drawing files for the printed
parts are available on the Kronos
Robotics website. I will list links
later in the article.

By Michael Simpson

54 SERVO 12.2013

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